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LibC: Optimize qsort

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Apply same optimizations as to BAN quick sort!
This commit is contained in:
Bananymous
2026-05-13 04:36:13 +03:00
parent d181f9e553
commit d345f96387
1 changed files with 46 additions and 19 deletions
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65
userspace/libraries/LibC/stdlib.cpp
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@@ -780,46 +780,73 @@ static void qsort_swap(void* lhs, void* rhs, size_t width)
uint8_t* ulhs = static_cast<uint8_t*>(lhs);
uint8_t* urhs = static_cast<uint8_t*>(rhs);
uint8_t buffer[64];
uint8_t temp[64];
while (width > 0)
{
const size_t to_swap = BAN::Math::min(width, sizeof(buffer));
memcpy(buffer, ulhs, to_swap);
const size_t to_swap = BAN::Math::min(width, sizeof(temp));
memcpy(temp, ulhs, to_swap);
memcpy(ulhs, urhs, to_swap);
memcpy(urhs, buffer, to_swap);
memcpy(urhs, temp, to_swap);
width -= to_swap;
ulhs += to_swap;
urhs += to_swap;
}
}
static uint8_t* qsort_partition(uint8_t* pbegin, uint8_t* pend, size_t width, int (*compar)(const void*, const void*))
struct qsort_pair
{
uint8_t* pivot = pend - width;
uint8_t* p1 = pbegin;
for (uint8_t* p2 = pbegin; p2 < pivot; p2 += width)
uint8_t* lt;
uint8_t* gt;
};
static qsort_pair qsort_partition(uint8_t* pbegin, uint8_t* pend, size_t width, int (*compar)(const void*, const void*))
{
uint8_t* pivot = pbegin + (pend - pbegin) / width / 2 * width;
uint8_t* lt = pbegin;
uint8_t* eq = pbegin;
uint8_t* gt = pend;
while (eq < gt)
{
if (compar(p2, pivot) >= 0)
continue;
qsort_swap(p1, p2, width);
p1 += width;
const int comp = compar(eq, pivot);
if (comp < 0)
{
qsort_swap(eq, lt, width);
if (pivot == lt)
pivot = eq;
lt += width;
eq += width;
}
else if (comp > 0)
{
gt -= width;
qsort_swap(eq, gt, width);
if (pivot == gt)
pivot = eq;
}
else
{
eq += width;
}
}
qsort_swap(p1, pivot, width);
return p1;
return { lt, gt };
}
static void qsort_impl(uint8_t* pbegin, uint8_t* pend, size_t width, int (*compar)(const void*, const void*))
{
if ((pend - pbegin) / width <= 1)
if (pbegin + width >= pend)
return;
uint8_t* mid = qsort_partition(pbegin, pend, width, compar);
qsort_impl(pbegin, mid, width, compar);
qsort_impl(mid + width, pend, width, compar);
auto [lt, gt] = qsort_partition(pbegin, pend, width, compar);
qsort_impl(pbegin, lt, width, compar);
qsort_impl(gt, pend, width, compar);
}
void qsort(void* base, size_t nel, size_t width, int (*compar)(const void*, const void*))
{
if (width == 0)
if (width == 0 || nel <= 1)
return;
uint8_t* pbegin = static_cast<uint8_t*>(base);
qsort_impl(pbegin, pbegin + nel * width, width, compar);